SE 453,589 describes a device with a load lift, comprising an operation device, which can be influenced by a driving means, and which is located between a load and the driving means. The driving means comprises a rotary magnet motor, which is arranged to be controlled by electronics or other means and which can be connected to a sensor in the form of a piezoelectric crystal included in said manually easily influenced operation means. The device is simple and functions effectively without any requirements for a large muscular strength with the user. However, this construction implies that force is transmitted directly from the handle to the sensor, which may imply problems, above all as the sensor thereby easily can be damaged because of an overload. Further, it is difficult to reach an even sensitivity, and therefore the running action may be uneven.
Also, SE 453,589 describes a device with a load lift, comprising an operation means, which can be influenced by a driving means, and which is situated between a load and the driving means. Here, the driving means is arranged so that it is influenced by the lateral motion of the lifting wire rope in order to be able to move the carried load with the associated load in the corresponding direction at the desired occasions, e.g. when the loading staff is manually operating the load and influences the same in the direction which you want to move the load by means of the driving means in question. Potentiometers are mentioned as an example of position sensor s.
Sensor s operating without any appreciable force being transmitted from a movable component to the sensor are previously known. For instance, DE 195 45,923 A1 describes an inductive sensor in the form of a piston-cylinder device, where the piston comprises a through-hole where a ferromagnetic core is arranged. The core is surrounded by three coils. The axial motion between the piston and the cylinder creates a relative movement between the core and the coils, which is used for the measurement of the piston strokes. Similar sensor s are known through U.S. Pat. No. 3,654,549, which describes a device for the inductive measurement of the motion of a piston in a cylinder arranged in an injection moulding machine, GB 2 011 629 A, which shows a device for the monitoring of the operation of a piston- and cylinder unit, and EP 0 823 560 A1, which describes a hydraulic control unit comprising a position sensor.
In the four last mentioned documents, it is, thus described, how a core moves to and fro inside coils, and that one uses the relative movement between the core and the coils to get results, such as piston strokes and the motion of a piston, through inductive measurement, which shows that the basic principle to perform measurements on a core moving inside coils is also known, but applied within fields far from the field of the present invention.